[R] selecting columns based on partial names

[Chris Dolanc]

Hello,

I have a data frame with > 5000 columns and I'd like to be able to make 
subsets of that data frame made up of certain columns by using part of 
the column names. I've had a surprisingly hard time finding something 
that works by searching online.

For example, lets say I have a data frame (df) of 2 obs. of 6 variables. 
The 6 variables are called "1940_tmax", "1940_ppt", "1940_tmin", 
"1941_tmax", "1941_ppt", "1941_tmin". I want to create a new data frame 
with only the variables that have "ppt" in the variable (column) name, 
so that it looks like this:

plot name    1940_ppt    1941_ppt
774-CL                    231               344
778-RW                  228               313

Thanks.

-- 
Christopher R. Dolanc
Post-doctoral Researcher
University of California, Davis &
University of Montana